The present invention relates to a retractable antenna system for electrical devices. The invention is particularly useful with respect to the retractable antenna system described in our U.S. Pat. No. 5,204,687, and application Ser. No. 08/485,992 filed Jul. 6, 1995 now U.S. Pat. No. 5,606,327, and is therefore described below with respect to such antenna systems.
The above-cited patent and copending application disclose retractable antenna systems for electrical devices, particularly cordless telephones, which antenna systems include a rod antenna (sometimes called a whip), and a coil antenna carried by the outer end of the rod antenna. The rod antenna is movable to either a retracted position within the housing wherein substantially only the coil antenna is disposed externally of the housing, or to an extended position externally of the housing wherein substantially the complete rod antenna and coil antenna are disposed externally of the housing. In the preferred embodiments therein described, the rod antenna and coil antenna are pretuned to the same frequency such that in the extended position of the antenna system, the rod antenna is enabled for use in long range operation, and in the retracted position of the antenna system, the coil antenna is enabled for use in short range operation.
In such constructions, the coil antenna carried at the outer end of the rod antenna is of substantial mass. Therefore, when the rod antenna is in its extended position, the long length of the rod antenna, together with the substantial mass of the coil antenna at the outer end of the rod antenna, cause the rod antenna to become very floppy, i.e., to readily flex or vibrate with substantial displacement magnitudes. This may be very disturbing to the user carrying the electrical device and attached antenna assembly; moreover, it can also result in breakage of the rod antenna.